A phase II trial to evaluate the efficacy of panitumumab combined with fluorouracil-based chemotherapy for metastatic colorectal cancer: the PF trial

Purpose Fluorouracil monotherapy, instead of the FOLFOX or FOLFIRI regimen, is administered to patients intolerant to oxaliplatin or irinotecan because of their adverse effects. A prospective clinical trial was designed to evaluate the efficacy and safety of fluorouracil monotherapy combined with panitumumab administered to patients with KRAS wild-type (WT) metastatic colorectal cancer (mCRC) intolerant to oxaliplatin and irinotecan. Screening for potential serum biomarkers to predict early therapeutic responses was conducted. Methods This single-arm, open-label multicenter phase II trial recruited patients with KRAS WT mCRC from 16 institutes between January 2012 and October 2014. Panitumumab (6 mg/kg) was intravenously administered every 2 weeks, combined with fluorouracil monotherapy, in 2-week cycles. The primary objective was overall response rate, and secondary endpoints included disease-control rate, progression-free survival, overall survival, toxicity, and blood-test data. Results Forty patients (male, 65.0%; median age, 74 years; colon cancer, 72.5%) met eligibility criteria and received 7 cycles (median) of fluorouracil chemotherapy combined with panitumumab. There were no treatment-related deaths. Median time to treatment failure was 3.2 months. 23 (57.5%) patients experienced at least one adverse effect ≥ grade 3. The response rate was 10.0% (95% confidence interval 2.8–23.7%). Median progression-free survival and overall survival were 4.3 and 11.3 months, respectively. Total lactase dehydrogenase (LDH) levels and those of LDH-4 and LDH-5, quickly changed with disease reduction or progression. Conclusions Fluorouracil monotherapy combined with panitumumab was safely administered to patients with KRAS WT mCRC intolerant to oxaliplatin and irinotecan. Serum LDH levels may predict early responses.